POLYSTIRA TO PAN-TROPICA: DEVELOPING STRATEGIES FOR ANALYSING MOLLUSCAN HYPERDIVERSITY

Over the past decade large-sale biodiversity expeditions, together with re-examination of existing collections holdings, have demonstrated living marine tropical molluscs to be much more taxonomically diverse than ever previously suspected. Predominantly this new diversity is located at the tree tips – genera and species – frequently comprising morphologically tightly structured (‘semi-cryptic’) species. These appear to be scattered widely across the molluscan tree. A similar relationship of taxonomic and morphological diversity very likely applied during the Neogene. Integrative studies of the morphologically conservative but hyperdiverse (>120 living species, 85% undescribed) neotropical snail Polystira (Oligocene-Recent) show that optimally it may be possible to delimit extinct species conceptually equivalent to living molecularly-delimited ones. The flipside is that most traditional fossil ‘species’ would be considered to be supraspecific groupings and not necessarily clades in the Recent. Is this exceptional or are these issues widespread? Based on my experience of systematizing and analysing Neogene molluscan diversity of tropical America for the Panama Paleontology Project, I discuss whether ‘true-species’ level precision is obtainable or necessary for pantropical palaeodiversity and biogeographic studies, and if not, what sort of supraspecific taxonomic and morphologic unit might usefully take its place.

Transoceanic, not even pantropical, systematic syntheses containing such supraspecific taxa are very few. So how then do we discover these analysable units? One way is to construct a collaborative on-line morphological and systematic database using a social networking tool (e.g. Scratchpads: http://scratchpads.eu/) to tie taxonomic expertise, morphological data and ontologies, with molecular trees, literature, museum types and other vouchers in order to generate these analysable clades. For selected taxa more detailed ‘true species’-level case studies would give further insights. This work would help train a generation of workers committed to a truly integrative systematics (extinct + extant). Using such tools as data aggregators will help build a pantropical molluscan dataset for uncovering systematic, palaeobiogeographic and macroecological patterns.